Postprandial Glycogen Content Is Increased in the Hepatocytes of Human and Rat Cirrhotic Liver

Abstract

Chronic hepatitises of various etiologies are widespread liver diseases in humans. Their final stage, liver cirrhosis (LC), is considered to be one of the main causes of hepatocellular carcinoma (HCC). About 80–90% of all HCC cases develop in LC patients, which suggests that cirrhotic conditions play a crucial role in the process of hepatocarcinogenesis. Carbohydrate metabolism in LC undergoes profound disturbances characterized by altered glycogen metabolism. Unfortunately, data on the glycogen content in LC are few and contradictory. In this study, the material was obtained from liver biopsies of patients with LC of viral and alcohol etiology and from the liver tissue of rats with CCl4-induced LC. The activity of glycogen phosphorylase (GP), glycogen synthase (GS), and glucose-6-phosphatase (G6Pase) was investigated in human and rat liver tissue by biochemical methods. Total glycogen and its labile and stable fractions were measured in isolated individual hepatocytes, using the cytofluorometry technique of PAS reaction in situ. The development of LC in human and rat liver was accompanied by an increase in fibrous tissue (20- and 8.8-fold), an increase in the dry mass of hepatocytes (by 25.6% and 23.7%), and a decrease in the number of hepatocytes (by 50% and 28%), respectively. The rearrangement of the liver parenchyma was combined with changes in glycogen metabolism. The present study showed a significant increase in the glycogen content in the hepatocytes of the human and the rat cirrhotic liver, by 255% and 210%, respectively. An increased glycogen content in cells of the cirrhotic liver can be explained by a decrease in glycogenolysis due to a decreased activity of G6Pase and GP.

Dynamics of the Glycogen β-Particle Number in Rat Hepatocytes during Glucose Refeeding

“…Using the method described in detail in the article by Bezborodkina et al, 2021 [ 18 ], the number of glucose residues in β-particles was determined at different stages of glycogen accumulation after administration of glucose to starved rats. Briefly, the technique is based on: Detection of cells with the lowest glycogen content in the population of hepatocytes; The assumption that glucose residues on the outer tiers of β-particles are associated with key enzyme proteins directly involved in glycogenesis and glycogenolysis, and residues located on the inner tiers of β-particles are free from proteins; The assumption that glycogen synthase, glycogen phosphorylase and the debranching enzyme make up the majority of the proteins of the β-particle and, in accordance with their diameter, are associated with 7, 9 and 9 glucose residues.…”

“…In some pathologies in humans and animals (for example, glycogen storage disease type 1a, liver cirrhosis), associated with a strong weakening of the activity of glucose-6-phosphatase or its complete absence in the liver, a large amount of glycogen accumulates in hepatocytes. The glycogen content in cells can exceed the regular level several times [ 18 , 47 , 48 ]. However, it remains unclear whether the accumulation of glycogen in these diseases occurs due to an increase in the number of β-particles in hepatocytes or due to an increase in the number of glucose residues in the particles (filling new tiers), and, accordingly, an increase in their size.…”

“…A percentage of the parenchyma (R) in the sections were assessed by an AxioVert 200M microscope (Carl Zeiss, Jena, Germany) equipped with a 10×/0.30 objective and a digital camera Leica DFC420C (Leica Microsystems, Wetzlar, Germany). For each animal, 20–30 fields of vision were analyzed using the ImageJ software (National Institutes of Health, Bethesda, Maryland, USA, , accessed on 1 July 2022) [ 18 ].…”

“…It is believed that a completely formed glycogen macromolecule (β-particle) has a diameter of 42–44 nm and a molecular weight of ~10 7 Da and includes ~55,000 glucose residues connected by α-(1→4) and α-(1→6) glycosidic bonds arranged in 12 tiers [ 9 , 10 , 11 , 12 ]. In addition to the polysaccharide part, in the center of the β-particle there is glycogenin, a self-glycosylating protein, and on the glycogen molecule surface there are proteins that are directly involved in the attachment–detachment of glucose residues or in the regulation of these processes [ 13 , 14 , 15 , 16 , 17 , 18 , 19 ]. All these proteins are an integral part of the spatial structure of β-particles and together can make up to 80% of its mass [ 20 ].…”

Unveiling the Link: Exploring Mitochondrial Dysfunction as a Probable Mechanism of Hepatic Damage in Post-Traumatic Stress Syndrome

“…The tissue sections were deparaffinized in xylene and rehydrated through graded ethanol. Histochemical staining was performed using standard techniques to reflect glycogen deposition in the liver [ 89 ]. Sections were oxidized with periodic acid for 10 min and stained with Schiff reagent for 15 min at room temperature.…”